Amir Khan boxed 40 miles from where he grew up on Saturday night (probably for the last time, as he resets his compass for America) and won a close fight against an opponent, Julio Díaz, who accepted defeat graciously, even though he had the local favourite over in round four and out on his feet in the 11th round. If all fighters were as magnanimous in defeat, it would be a much better sport, although possibly not as interesting for those addicted to acrimony.

Later that evening, 7,000 miles away in Buenos Aires, Martin Murray, of St Helens, twice knocked down the world middleweight champion and Argentinian sporting god, Sergio Martínez, but was credited with only the first of those, due to the ineptness in the 10th round of the Italian referee, Massimo Barrovecchio, and so the challenger lost a close fight, 115-112 on all cards. He, too, chose not to complain.

I have no access to the scorecard, but, had Murray been given a second 10-8 round, he might have earned a draw – to go with his sharing of the points with another world champion, Felix Sturm. As it is, he emerged with credit but no title.

And you will want to know, of course, where the judges came from. For Murray-Martínez, Nicolas Hidalgo, a well-travelled WBC favourite, calls Venezuela home; Alejandro Rochin is a Mexican living in California, whose judgment was not needed when Khan stopped Carlos Molina in Los Angeles before Christmas; and Rey Danseco is a Filipino who got it right for Saúl Alvarez against Austin Trout in Texas last weekend.

For Khan-Díaz, none of the officials – the referee, Marcus McDonnell, or the judges, Phil Edwards, Steve Gray and Terry O'Connor – had to travel further than Twickenham. It was set at a catchweight of 143lb, and yet it was over 12 rounds, a curiosity with no belt at stake. Had it been over 10 rounds, as convention dictates, there would have been no controversy, as by that point Khan was comfortably ahead.

While there was no hint or suggestion of impropriety, there were partisan suspicions in each fight that the home boxer had a subliminal edge.

Whether or not you thought either loser was hard done by – I had it as a draw in Sheffield, although I'm open to persuasion that Khan nicked it in the last round and, after watching the tape, I thought a below-par Martínez kept his title by a point – there is a more fundamental issue at stake: why should the visiting fighter, a designated underdog, have to do more than the champion to get the decision?

Because that was the almost universal wail afterwards, among respected commentators and a tidal wave of angry punters on Twitter. In Sheffield, Díaz admitted he "didn't do enough" to overturn that home advantage, without implying any skulduggery.

Yet nowhere in the admittedly anarchic laws and regulations of boxing is it written that the "house fighter" should have any advantage purely by holding the title or fighting in his home town. It nevertheless is a widely held fallacy, so ingrained in the culture of the business that few people, aggrieved or otherwise, dispute it. It's the way it is, mate.

If you go into the champion's backyard, the mantra goes, it is not enough to box your own fight and win on merit, you have to do something extra, "take the fight to him". Neither can you "expect any favours" from the officials.

And thus it has become acceptable for a challenger to be handicapped before he has thrown a punch. There is no logic to it. In no other sport that I can think of is there such a blatant bias. Cricket, perhaps, comes close when groundsmen prepare pitches favourable to the home team – but that not only evens itself out over time but makes interesting demands on the players to adapt to difficult and unfamiliar conditions, such as seaming wickets in England, turners in India and rock-hard strips for fast bowlers in Australia – or at the Waca, at least.

I suspect, in boxing, this in-built advantage for the champion is an historical leftover from bareknuckle days, when the acknowledged holder of the title issued a challenge to anyone who fancied his chances.

John L Sullivan is said, by legend, to have roused drinkers around Boston and New York with the loud provocation, "I can whip any sonofabitch in the house". And he could, but we should have come a long way from the days when the dominant party could persuade sometimes inadequate (but grateful) opponents to share space with him in an uneven contest.

Today, we have weight divisions, gloves and, supposedly, incorruptible officials. Yet we know there are ways for the favoured fighter and his connections to manipulate an edge. Many champions hand-pick smaller opponents (and bulk up outrageously after the day-before weigh-in), a few have been found with loaded gloves.

Scoring in boxing is the insoluble bugbear. In Khan's fight there was a case to score at least a couple of rounds even, including the last, which most observers gave to Khan. Yet judges are urged to make a call one way or another, even when a round is desperately hard to call, and that turns many a fight into a lottery.

A judge might lean towards the fighter in the "left-hand column" without thinking – or, in some cases, maybe the prospect of another nice trip coming up.

The point needs emphasising that Murray did not make a fuss, although his fans were furious. He reckoned he lost, fair and square. Nor was Díaz put out. He admitted he could not finish the job against Khan when he had him going in the 11th and gave credit to the winner for improved footwork when in trouble, hard-to-read switches of pace and good use of angles.

Oddly, however, the British loser on the night came away with more to savour from his performance than the British winner. Murray, for the second time, pushed a genuine world champion all the way; Khan, worryingly, looked vulnerable again, this time against a former world champion whose best years are some way behind him.

There is, of course, one way to take all doubt out of these equations. Even John L Sullivan knew that.